The invention relates to an apparatus for a security system in accordance with the kind defined in more detail in the preamble of Claim 1. The invention also relates to a mobile identification transmitter according to Claim 9, a method according to Claim 11, a security system in accordance with Claim 16 and a vehicle in accordance with Claim 18.
It is known from the prior art that mobile identification transmitters are used for communication with a vehicle, in particular a motor vehicle, for example to effect a keyless activation of a locking mechanism of the vehicle (e.g. for opening the doors). Thereby, the mobile identification transmitter (ID transmitter) is used for authentication with the vehicle, wherein for example a locking mechanism of the vehicle is released only in the event of a positive authentication. In the context of the authentication process, for example authentication data (e.g. with a security code) are transmitted by the ID transmitter over a wireless link to a security system of the vehicle. There is also an increasing market penetration of electronic security systems for locking devices of vehicles, which have e.g. a “passive keyless entry” or “keyless go” functionality. In contrast to conventional security systems, such passive access systems do not require active operation of the mobile ID transmitter (such as the actuation of a button in the ID transmitter) by an operator to perform locking and unlocking. In order also to initiate an authentication query without active operation, a wake-up signal is sent to the ID transmitter, for example by the vehicle or the security system, over a wireless link. This wake-up signal, which is in particular an initialization signal, is detected by the external ID transmitter outside the vehicle, whereupon the latter then carries out an identification check with the vehicle over an (additional) wireless or communication link. For the communication between the vehicle and the ID transmitter, and in particular for transferring the wake-up signal, it is usual to use e.g. an LF wireless connection (Low-Frequency Radio Connection) for example with a frequency of essentially 125 kHz.
It has proved to be a disadvantage that the functionality and reliability of the security system, and in particular of the communication between the vehicle (or security system) and the ID transmitter over a radio link can be severely impaired due to effects such as interference frequencies.
If, for example, an inductive charging process takes place simultaneously to the communication, either of the vehicle or of a vehicle located nearby, then the communication between the security system and the mobile ID transmitter is seriously disrupted due to frequency superposition with the charging frequency, so that a reliable keyless activation of the vehicle locking mechanism by the operator is not feasible. This can then result in, for example, a faulty transmission, or the transmission of the radio signal over the radio link may be completely inhibited.